Jacobson nerve schwannoma

Jacobson nerve schwannomas are rare, benign middle ear tumors that involve the eponymous tympanic branch of the glossopharyngeal nerve. They appear as a mass on the cochlear promontory and enlargement of the inferior tympanic canaliculus .

Clinical presentation

Patients may present with hearing loss , otalgia , or pulsatile tinnitus . Otoscopic exam reveals a pale, non-pulsatile mass in the middle ear cavity .

Pathology

General pathologic features are described separately: schwannoma.

Radiographic features

CT

CT demonstrates the tumor with secondary bony changes :

• soft tissue mass in the middle ear cavity based at the cochlear promontory
• possible erosion of the cochlear promontory
• expansion of the inferior tympanic canaliculus
• no significant enhancement

MRI

The signal characteristics are typical of schwannomas elsewhere :

• T1: hypointense
• T2: hyperintense
• T1 C+: homogeneous moderate enhancement

Differential diagnosis

• glomus tympanicum paraganglioma (most common tumor at the cochlear promontory)
  • more intensely enhancing
  • more permeative bone changes
  • red and pulsatile on otoscopy
• facial nerve schwannoma (most common middle ear schwannoma)
  • distinct location along facial nerve canal